According to current estimates, 80,764 people in America are waiting for organ transplantation. All organ-transplanted patients undergo an extensive immunosuppression therapy with drugs, such as cyclosporine (Neoral®, Sandimmune®), prednisone (Novo Prednisone®, Apo Prednisone®), azathioprine (Imuran®), tacrolimus or FK506 (Prograf®), mycophenolate mofetil (CellCept®), OKT3 (Muromorab CO3®, Orthoclone®), or ATGAM & Thymoglobulin. While the use of these drugs has improved the chances for survival in patients receiving organ transplants, three-year mortality rates range from 10-40% and chronic rejection remains a serious issue.
Almost all patients experience at least one episode of rejection following transplant surgery. Chronic rejection is a slow, progressive process that usually begins inside the transplant organ's blood vessels, which are lined by donor cells that interact with host white blood cells in the bloodstream. Over time, as a result of inflammation and rejection reactions, scar tissue can accumulate inside these vessels, reducing or preventing blood flow into the filter and chemical plant portions of the kidney. If blockages become widespread, the organ becomes compromised owing to lack of oxygen and nutrients. Approximately 10 percent of kidney transplants fail each year due to chronic rejection, graft dysfunction and kidney toxicity, causing the patient to need dialysis and often a new organ.
While the current therapies used to combat rejection have resulted in improved transplant outcomes, they are only effective if used on a continuous basis. Consequently, most patients must maintain their regimen of anti-rejection drugs for the rest of their lives. In addition, many of the currently approved drugs are highly toxic and produce severe adverse side effects when used regularly leading to a high rate of patient morbidity following the transplant. Adverse effects from these drugs may include fever, nausea, edema, and a wide range of specific organ toxicity. Because anti-rejection drugs are immunosuppressive, patients also run a high risk of developing concomitant infections. Adverse drug interactions are also common and administration of current medications must be carefully monitored and controlled. Thus, there is a significant unmet need for improved anti-rejection drugs which demonstrate both efficacy and better long-term tolerability.
One key strategy for reducing the risk of organ transplant rejection is to more effectively modulate the body's natural immune response to the new organ. Recent therapeutic strategies to combat organ allograft rejection have focused on T cell signaling pathways and the molecules that comprise them. While some pharmaceuticals have shown promise in blocking acute rejection, chronic graft destruction and permanent allograft acceptance in the absence of continuous immune suppression is problematic. Recent data now suggest T cells hold the key to generation of transplantation tolerance and alleviation of long-term drug intervention.
Lactoferrin is a single chain metal binding glycoprotein. Many cell types, such as monocytes, macrophages, lymphocytes, and brush-border cells in the intestine, are known to have lactoferrin receptors. Lactoferrin is found mainly in external secretions of mucosal epithelia such as breast milk, saliva, tears, bile, and pancreatic fluid and has a wide array of functions related to host immune response mechanisms. For example, lactoferrin has been reported to modulate a number of key cytokines, chemokines or other molecules that control the immune response including IL-2, IL-10, IL-18, INF-γ, TNF-α, MIP3-α and NF Kappa-B among others. In addition, lactoferrin has been shown to modulate the Th1/Th2 immune response pathways as well as activate polymorphonuclear neutrophils (PMN) and regulate granulopoeisis.
Recombinant human lactoferrin has previously been described as being purified after expression in a variety of prokaryotic and eukaryotic organisms including aspergillus (U.S. Pat. No. 6,080,559), cattle (U.S. Pat. No. 5,919,913), rice, corn, Saccharomyces (U.S. Pat. No. 6,228,614) and Pichia pastoris (U.S. Pat. Nos. 6,455,687, 6,277,817, 6,066,469). Also described are expression systems for the expression of full-length human lactoferrins (e.g., U.S. Pat. No. 6,100,054). In all cases, part of the teaching is expression of the full length cDNA and purification of the intact protein whose N-terminal, after processing of the leader peptide, is the amino acid glycine. Nuijens et al. (U.S. Pat. No. 6,333,311) separately describe variants of human lactoferrin but their focus is limited to deletion or substitution of arginine residues found in the N-terminal domain of lactoferrin.
The present invention is the first to use a lactoferrin composition as a means of immunosuppressant therapy to prevent organ rejection and graft-versus-host-disease.